<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <!-- <script>
    console.log('1')
    setTimeout(() => {
      console.log('2')
    }, 0)
    console.log('3')
  </script> -->

  <button>测试xhr是异步函数</button>
  <script>
    document.querySelector('button').addEventListener('click', function () {
      console.log('1')

      const xhr = new XMLHttpRequest()
      xhr.open('post', 'http://ajax-api.itheima.net/api/login')
      xhr.setRequestHeader('content-type', 'application/json')

      xhr.addEventListener('load', function () {
        //   console.log(xhr.response)
        //   console.log(JSON.parse(xhr.response))
        console.log('2')
      })
      let obj = {
        username: 'admin',
        password: '123456',
      }
      xhr.send(JSON.stringify(obj))

      console.log('3')
    })
  </script>
</body>

</html>